Production method and production facility for steel sheet pile with flanges

ABSTRACT

To suppress the occurrence of a defective shape such as a flange wave or the like by reverse rolling so as to improve the product dimension accuracy and stability of rolling. A production method for forming a steel sheet pile with flanges from a material to be rolled by caliber roll rolling, includes a step of performing reverse rolling on the material to be rolled by a same caliber, wherein: the step of performing reverse rolling includes a step of forming first flange parts across a neutral line and second and third flange parts arranged on both sides of the first flange parts; the caliber includes first flange facing portions for forming the first flange parts, second flange facing portions for forming the second flange parts, and third flange facing portions for forming the third flange parts; and an inclination angle of the first flange facing portion with respect to a horizontal plane is larger than inclination angles of the second and third flange facing portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2017-073578, filed in Japan onApr. 3, 2017, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a production method and a productionfacility for a steel sheet pile with flanges such as a hat-shaped steelsheet pile, a U-shaped steel sheet pile or the like.

BACKGROUND ART

Conventionally, the production of a steel sheet pile having joints atboth ends of a hat shape or the like is performed by a caliber rollingmethod. Known as a general process of the caliber rolling method is,first, heating a rectangular material to a predetermined temperature ina heating furnace and sequentially rolling the rectangular material by arough rolling mill, an intermediate rolling mill, and a finish rollingmill including calibers. As the caliber rolling method, a technique ofarranging a plurality of calibers at rolls in rough rolling,intermediate rolling, and finish rolling and performing rolling in oneto two passes in each of the calibers to produce a hat-shaped steelsheet pile is disclosed, for example, in Patent Document 1.

Besides, a technique of constituting a caliber to balance web and flangeelongations in the production of a U-shaped steel sheet pile andperforming rolling by reciprocating a material to be rolled a pluralityof times in the same caliber is disclosed, for example, in PatentDocument 2. Besides, a technique for the purpose of reducing the placingresistance in constructing a steel sheet pile is disclosed and aconfiguration in which a gradually inclined part is provided at a flangepart is proposed, for example, in Patent Document 3.

Further, a production technique for a Z-shaped steel sheet pileincluding a step of shaping a pre-form having two flange/web transitionsections parallel to a rolling plane and a middle section inclined withrespect to the rolling plane near a neutral line is disclosed, forexample, in Patent Document 4.

As described above, the caliber rolling method and the technique ofperforming rolling by reciprocating the material to be rolled aplurality of times in the same caliber (so-called one-calibermultiple-pass rolling) are conventionally invented as the productionmethod for a steel sheet pile.

PRIOR ART DOCUMENT

[Patent Document]

-   Patent Document 1: Japanese Laid-open Patent Publication No.    2006-88176-   Patent Document 2: Japanese Laid-open Patent Publication No.    S60-44101-   Patent Document 3: Japanese Laid-open Patent Publication No.

2004-76580

-   Patent Document 4: Japanese Laid-open Patent Publication No.    H8-224634

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the above conventional caliber rolling method exemplified inthe above Patent Document 1, the rolling in one to two passes in onecaliber is performed at the rough rolling, the intermediate rolling stepto the finish rolling step with the flange set to a linear state atsubstantially the same angle as that of the product but, in particular,in the case where the flange width is large and the sheet thickness issmall, when the reverse rolling is performed, the elongation at eachpart in the cross section of the material to be rolled cannot bebalanced, causing a flange wave in some cases. Note that the “caliber”in the description is a gap formed between upper and lower caliber rollsand indicates a portion through which the material to be rolled ispassed and rolled. Hereinafter, as long as the grooves on the rollsforming the caliber are the same if the distance between the upper andlower caliber rolls varies, the caliber will be explained while beingcalled “the same caliber”. Further, the “reverse rolling” in thedescription means a step of repeatedly performing rolling byreciprocating the material to be rolled in a plurality of passe whilegradually narrowing the roll gap in the same caliber constituted of theupper and lower caliber rolls.

Besides, in the technique disclosed in the above Patent Document 2, inthe case of performing rolling that takes large elongation, inparticular, for a large-sized steel sheet pile having a large flangewidth and a small flange thickness as compared with the conventionalone, like a hat-shaped steel sheet pile, a defective shape such as aflange wave or the like occurs even if balancing the elongationsdescribed in the above Patent Document 2, so that the stable rolling andshaping is difficult and a product defective shape possibly occurs.Further, the balancing condition appropriate for suppressing theoccurrence of the defective shape such as a flange wave or the likecannot be realized in some cases in the constraint of the rolling mill.In recent years, in fact, a steel sheet pile in a large cross sectionhaving a large height and a small sheet thickness is demanded from theviewpoint of economy and construction property, and a furtherimprovement of technique is required in the production of thelarge-sized steel sheet pile.

Besides, regarding the technique disclosed in the above Patent Document3, it is stated that a gradually inclined part is provided at a part (atone or more places of a corner part formed by an end flange part and aweb part and a middle part of a web part) of a web part (defined as aflange part in the present invention) to reduce the placing resistanceand improve the construction property, but the defective shape such as aflange wave or the like in the production process is not mentioned atall. A further improvement of technique regarding realization of thesuppression of the defective shape and the realization of stable rollingand shaping and so on in the production of the large-sized steel sheetpile is demanded.

Besides, the technique disclosed in the above Patent Document 4 isconsidered to be a technique of performing one-caliber one-pass rolling,and there is no description of performing so-called reverse rolling ofperforming a plurality of passes while gradually narrowing the gapbetween the upper and lower rolls in the same caliber. This isconsidered to be because if the reverse rolling is performed in the samecaliber in the technique described in Patent Document 4, the elongationbecomes nonuniform at each part in the cross section, metal flow occursto change the filling stage at the joint part and the elongation of aflange/web transition section becomes geometrically larger than theelongation at a middle section, resulting in that twist becomes morelikely to occur. In the case of performing one-caliber one-pass rolling,the caliber shape can be made into an optimum shape during one-passrolling, so that the problem such as a defective shape of the materialto be rolled caused by the caliber shape cannot arise. In short, in theabove Patent Document 4, the occurrence of the flange wave possiblyoccurring during the reverse rolling is not mentioned at all and thesuppress of the flange wave is not mentioned at all as a matter ofcourse.

Hence, in consideration of the above circumstances, an object of thepresent invention is to provide a production technique for a steel sheetpile with flanges, capable of suppressing the occurrence of a defectiveshape such as a flange wave or the like by reverse rolling so as toimprove the product dimension accuracy and stability of rolling.

Means for Solving the Problems

To achieve the above object, according to the present invention, thereis provided a production method for forming a steel sheet pile withflanges from a material to be rolled by caliber roll rolling, theproduction method including a step of performing reverse rolling on thematerial to be rolled by a same caliber, wherein: the step of performingreverse rolling includes a step of forming first flange parts across aneutral line and second and third flange parts arranged on both sides ofthe first flange parts; the caliber includes first flange facingportions for forming the first flange parts, second flange facingportions for forming the second flange parts, and third flange facingportions for forming the third flange parts; and an inclination angle ofthe first flange facing portion with respect to a horizontal plane islarger than inclination angles of the second and third flange facingportions.

It is adoptable that the step of performing reverse rolling includes astep of forming a web corresponding part and arm corresponding parts;the caliber includes a web facing portion for forming the webcorresponding part and arm facing portions for forming the armcorresponding parts; the caliber includes web-side flange facing portiongroups each including at least one of the second flange facing portionsand arm-side flange facing portion groups each including at least one ofthe third flange facing portions; and with respect to a straight linelinking a boundary part between the web-side flange facing portion groupand the web facing portion and a boundary part between the arm-sideflange facing portion group and the arm facing portion, the secondflange facing portion is in a protruding shape in a flange outsidedirection, and the third flange facing portion is in a protruding shapein a flange inside direction.

It is adoptable that rolling in which a flange elongation κf1 at thefirst flange part is smaller than flange elongations λf2, λf3 at thesecond flange part and the third flange part is performed in thecaliber.

It is adoptable that the step of forming the first flange parts, thesecond flange parts, and the third flange parts is an intermediaterolling step.

It is adoptable that the caliber has a caliber shape opened at both endparts in a width direction.

It is adoptable that the flange corresponding parts in a bent shapeformed in the material to be rolled by the step of forming the firstflange parts, the second flange parts, and the third flange parts arerolled and shaped into a desired flat shape by rolling in a caliber at astage subsequent to the step of forming the first flange parts, thesecond flange parts, and the third flange parts.

It is adoptable that rolling is performed in the caliber so that theflange elongation κf1 at the first flange part becomes a web elongationλw or less.

It is adoptable that the steel sheet pile is a hat-shaped steel sheetpile.

According to the present invention from another viewpoint, there isprovided a production facility for forming a steel sheet pile withflanges from a material to be rolled by caliber roll rolling, theproduction facility including a rolling mill which performs reverserolling on the material to be rolled by a same caliber, wherein: therolling mill which performs reverse rolling includes a caliber whichforms first flange parts across a neutral line and second and thirdflange parts arranged on both sides of the first flange parts; thecaliber includes first flange facing portions for forming the firstflange parts, second flange facing portions for forming the secondflange parts, and third flange facing portions for forming the thirdflange parts; and an inclination angle of the first flange facingportion with respect to a horizontal plane is larger than inclinationangles of the second and third flange facing portions.

It is adoptable that the rolling mill which performs reverse rollingincludes a caliber which forms a web corresponding part and armcorresponding parts; the caliber includes a web facing portion forforming the web corresponding part and arm facing portions for formingthe arm corresponding parts; the caliber includes web-side flange facingportion groups each including at least one of the second flange facingportions and arm-side flange facing portion groups each including atleast one of the third flange facing portions; and with respect to astraight line linking a boundary part between the web-side flange facingportion group and the web facing portion and a boundary part between thearm-side flange facing portion group and the arm facing portion, thesecond flange facing portion is in a protruding shape in a flangeoutside direction, and the third flange facing portion is in aprotruding shape in a flange inside direction.

It is adoptable that a flange elongation λf1 at the first flange part issmaller than flange elongations λf2, λf3 at the second flange part andthe third flange part in the caliber.

It is adoptable that the caliber is a caliber provided in anintermediate rolling mill.

It is adoptable that the caliber has a caliber shape opened at both endparts in a width direction.

It is adoptable to further include a subsequent-stage caliber whichrolls and shapes the flange corresponding parts in a bent shape formedin the material to be rolled by rolling in the caliber which forms thefirst flange parts, the second flange parts, and the third flange parts,into a desired flat shape.

It is adoptable that the flange elongation λf1 at the first flange partis a web elongation λw or less in the caliber.

It is adoptable that the steel sheet pile is a hat-shaped steel sheetpile.

Effect of the Invention

According to the present invention, it becomes possible to suppress theoccurrence of a defective shape such as a flange wave or the like byreverse rolling so as to improve the product dimension accuracy andstability of rolling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic explanatory view of a rolling line.

FIG. 2 is a schematic cross-sectional view illustrating the calibershape of a first caliber.

FIG. 3 is a schematic cross-sectional view illustrating the calibershape of a second caliber.

FIG. 4 is a schematic cross-sectional view illustrating the calibershape of a third caliber.

FIG. 5 is a schematic cross-sectional view illustrating the calibershape of a fourth caliber.

FIG. 6 is a schematic cross-sectional view illustrating the calibershape of a fifth caliber.

FIG. 7 is a schematic explanatory view of a caliber in a configurationobtained by modifying the third caliber, and (a) illustrating aschematic entire view and (b) illustrating an enlarged view near a placefacing a flange corresponding part.

FIG. 8 is a schematic explanatory view according to a modificationexample of the present invention.

FIG. 9 is an explanatory view of an example.

FIG. 10 is a schematic explanatory view according to a modificationexample of the present invention.

FIG. 11 is a schematic explanatory view according to a modificationexample of the present invention.

FIG. 12 is a schematic explanatory view according to a modificationexample of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be explainedreferring to the drawings. Note that, in the description and thedrawings, the same codes are given to components having substantiallythe same functional configurations to omit duplicated explanation. Notethat the explanation will be made assuming that a material to be rolledin a substantially hat-shaped steel sheet pile shape is rolled in aposture that the web is located below the flange (so-called U-posture)in the embodiment, and the scope of application of the present inventionextends, as a matter of course, to rolling in other postures (forexample, an inverted U-posture). Further, the scope of application ofthe present invention ranges over steel sheet pile products havingvarious flanges in a hat shape, a U-shape and so on, and a steel sheetpile product produced in the embodiment will be explained as ahat-shaped steel sheet pile product.

Besides, a material to be rolled A described below indicates a steelmaterial to be rolled in the case of producing the hat-shaped steelsheet pile product, steel materials to be passed on a rolling line L aregenerically called the material to be rolled A, and the material to berolled A in states that it has been subjected to reduction in rollingmills are described separately using different names (A1 to A5 describedbelow) as needed. The material to be rolled A is in a substantial hatshape, and is composed of a substantially horizontal web correspondingpart 3, flange corresponding parts 5, 6 connected to both ends of theweb corresponding part 3 at a predetermined angle, arm correspondingparts 8, 9 connected to ends of the flange corresponding parts 5, 6different from the sides thereof connected with the web correspondingpart 3, and joint corresponding parts 10, 11 connected to tips of thearm corresponding parts 8, 9. Note that end portions of the jointcorresponding parts 10, 11 are called claw parts 14, 15, respectively.Hereinafter, parts constituting the material to be rolled A will beillustrated and explained with the aforementioned respective codes.

Note that, regarding the material to be rolled A, the rolling directionis called a “longitudinal direction” of the material to be rolled, adirection perpendicular to the longitudinal direction and parallel witha rolling roll axis is called a “width direction” of the material to berolled, and a direction perpendicular to both the longitudinal directionand the width direction is called a “height direction” of the materialto be rolled, for explanation in this description. Further, a “thicknessreduction” of the material to be rolled indicates a sheet thicknessreduction in the sheet thickness direction of the material to be rolled.

First of all, the outline of the rolling line L being a basicconfiguration as a producing apparatus 1 for producing the hat-shapedsteel sheet pile will be explained. FIG. 1 is an explanatory view of therolling line L for producing the hat-shaped steel sheet pile, rollingmills provided on the rolling line L and so on. In FIG. 1, a rollingforward direction of the rolling line L is a direction indicated with anarrow, the material to be rolled A flows in the direction, rolling isperformed in caliber rolling mills (later-explained rough rolling mill,intermediate rolling mill, and finish rolling mill) on the line to shapea product. Note that a plurality of not-illustrated conveyor rolls areinstalled on the rolling line L, and the material to be rolled A isconveyed on the rolling line L by the conveyor rolls.

As illustrated in FIG. 1, on the rolling line L, a rough rolling mill(BD) 17, a first intermediate rolling mill (R1) 18, a secondintermediate rolling mill (R2) 19, and a finish rolling mill (F) 30 arearranged in order from the rolling upstream side.

On the rolling line L illustrated in FIG. 1, the material to be rolled Asuch as a slab, bloom or the like heated in a not-illustrated heatingfurnace (located on the upstream of the rolling line L) is rolled insequence in the rough rolling mill 17 to the finish rolling mill 30 toform into a hat-shaped steel sheet pile being a final product.

Next, the shape of the caliber provided in any of the rough rolling mill17, the first intermediate rolling mill 18, the second intermediaterolling mill 19, and the finish rolling mill 30 arranged on the rollingline L will be briefly explained in order from the upstream sidereferring to the drawings. Note that in FIG. 2 to FIG. 6 referred to inthe following explanation, the cross section of the material to berolled A when the reduction in each caliber is completed is illustratedwith one-dotted chain line for reference.

FIG. 2 is a schematic cross-sectional view of the caliber shape of thefirst caliber 49 (hereinafter, also described simply as a caliber 49).As illustrated in FIG. 2, the caliber 49 is composed of an upper caliberroll 45 and a lower caliber roll 48. The caliber 49 composed of theupper caliber roll 45 and the lower caliber roll 48 is provided, forexample, in the rough rolling mill 17, and the caliber rolling in thecaliber 49 performs the thickness reduction (namely, rough rolling) onthe whole material to be rolled A. More specifically, the caliberrolling of making the slab or the like heated to a predeterminedtemperature in the heating furnace closer to the substantial hat shapeis performed to shape a raw blank A1 illustrated with a one-dotted chainline in FIG. 2. Note that the rough rolling at this time may beperformed, for example, by reverse rolling in the same caliber 49.

Besides, FIG. 3 is a schematic cross-sectional view of the caliber shapeof a second caliber 59 (hereinafter, also described simply as a caliber59). As illustrated in FIG. 3, the caliber 59 is composed of an uppercaliber roll 55 and a lower caliber roll 58. The caliber 59 composed ofthe upper caliber roll 55 and the lower caliber roll 58 is provided, forexample, in the first intermediate rolling mill 18, and the caliberrolling in the caliber 59 performs the thickness reduction (namely,first intermediate rolling) on the whole material to be rolled A. In thecaliber 59, reduction of aligning the claw heights of the claw parts 14,15 to a desired height is also performed concurrently with the thicknessreduction, and more specifically, the caliber rolling of making the rawblank A1 carried out of the caliber 49 much closer to the hat shape isperformed. Thus, a first intermediate material A2 illustrated with aone-dotted chain line in FIG. 3 is shaped. Note that the rolling here isperformed, for example, by reverse rolling in the same caliber 59.

Besides, FIG. 4 is a schematic cross-sectional view illustrating thecaliber shape of a third caliber 69 (hereinafter, also described simplyas a caliber 69). As illustrated in FIG. 4, the caliber 69 is composedof an upper caliber roll 65 and a lower caliber roll 68. The caliber 69composed of the upper caliber roll 65 and the lower caliber roll 68 isprovided, for example, in the second intermediate rolling mill 19, andthe caliber rolling in the caliber 69 performs the thickness reduction(namely, second intermediate rolling) on the whole material to be rolledA. More specifically, the caliber rolling of making the firstintermediate material A2 carried out of the caliber 59 much closer tothe hat shape is performed, and thereby a second intermediate materialA3 illustrated with a one-dotted chain line in FIG. 4 is shaped. Thiscaliber 69 is in a shape having both end portions in the width directionopened, so that the claw parts 14, 15 of the material to be rolled A arein shapes extended in the width direction by the thickness reduction.Note that the rolling here is performed, for example, by reverse rollingin the same caliber 69.

FIG. 5 is a schematic cross-sectional view illustrating the calibershape of a fourth caliber 79 (hereinafter, also described simply as acaliber 79). As illustrated in FIG. 5, the caliber 79 is composed of anupper caliber roll 75 and a lower caliber roll 78. The caliber 79composed of the upper caliber roll 75 and the lower caliber roll 78 isprovided, for example, in the second intermediate rolling mill 19, andthe caliber 79 intensively performs, for example, shaping of the clawparts 14, 15 of material to be rolled A. More specifically, thereduction to perform the forming while aligning the claw heights of theclaw parts 14, 15 in the state extended in the third caliber 69 to adesired height is performed to shape a second intermediate material A4.Note that the rolling here may be reduction of the thickness.

Besides, FIG. 6 is a schematic cross-sectional view illustrating thecaliber shape of a fifth caliber 89 (hereinafter, also described simplyas a caliber 89). As illustrated in FIG. 6, the caliber 89 is composedof an upper caliber roll 85 and a lower caliber roll 88. The caliber 89composed of the upper caliber roll 85 and the lower caliber roll 88 isprovided, for example, in the finish rolling mill 30, and the caliber 89mainly performs bending forming (namely, finish rolling) of the clawparts 14, 15 on the material to be rolled A. More specifically, thereduction of making the second intermediate material A4 into a finishedmaterial A5 in the substantial hat shape (substantially hat-shaped steelsheet pile product shape). Note that, normally, the finish rolling isnot performed in reverse rolling but is performed by rolling in only onepass.

Thus, the material to be rolled A is subjected to caliber rolling ineach rolling explained referring to FIG. 2 to FIG. 6, and the finishedmaterial A5 is finally shaped.

Note that the configurations of the first caliber to the fifth caliberdescribed in the embodiment are examples and the configurations are notlimited to the illustrated forms, but, for example, the arrangementorder of the calibers, the caliber shape arranged in each rolling mill,and the increased/decreased arrangement of correction calibers forvarious calibers may be changed as needed according to conditions suchas the facility status, product dimensions and so on. Further, dependingon the kind of the raw material, it is also conceivable to separatelyprovide a caliber such as a preform caliber used for rough shapingprocess from the raw material.

According to the study of the present inventors, at an intermediaterolling step by the caliber 59 and the caliber 69 in the aboveproduction process, even when the rolling is performed while balancingthe elongation between the web corresponding part 3 and the flangecorresponding parts 5, 6, the relative sliding speed between thematerial to be rolled A (specifically, the flange corresponding parts 5,6) and the roll differs depending on a part because the upper and lowercaliber rolls are different in diameters of upper and lower rollsdepending on a part as illustrated in FIG. 3 and FIG. 4. At the flangecorresponding parts 5, 6, the elongation of the material to be rolled issuppressed by a peripheral speed difference between the upper and lowerrolls at a part where the difference between upper and lower rolldiameters is large, whereas the elongation is likely to occur at aposition corresponding to a pitch line where the diameters of the upperand lower rolls are equal (hereinafter, described a “neutral line”), sothat a compressive stress is likely to occur in the longitudinaldirection in the flange near the neutral line at a roll bite outlet and,in the case where the compressive stress exceeds a buckling limit, adefective shape so-called flange wave occurs at the flange correspondingparts 5, 6.

In particular, in the production of a large-sized steel sheet pile suchas a hat-shaped steel sheet pile having a high ratio of flangewidth/flange thickness, the elongation of the flange near the neutralline tends to be large relative to the elongation of the web, and thecompressive stress in the longitudinal direction acts on the middleparts of the flange corresponding parts 5, 6 from the inside of the rollbite. Further, the buckling limit stress also lowers, resulting in thatthe flange wave is remarkably likely to occur.

In the case of performing rolling in one pass by the same caliber,designing a caliber in a shape under consideration of the flangeelongation and the web elongation according to the relation with theshape of the preceding caliber can suppress the flange wave. However, ithas been found that in the case of performing rolling in two or morepasses by the same caliber, each elongation of the web correspondingpart, the flange corresponding part and the arm corresponding part isprescribed by the shape of the caliber in the rolling in the second andsubsequent passes, so that it is impossible to suppress the occurrenceof the flange wave in the middle of the reverse rolling even if theshape of the caliber is designed as in the prior art. For example, theresult of study has revealed that in the case where the reverse rollingis performed in the calibers 59, 69, the metal gathers at the middleparts (near the neutral line) of the flange corresponding parts 5, 6every rolling at the flange corresponding parts 5, 6, and a phenomenonof restoration of the flange thickness is likely to occur. If therestoration of the thickness occurs, the flange elongation increases inthe next pass and the flange wave undesirably becomes more likely tooccur.

Besides, comparing the caliber 59 and the caliber 69, the caliber 69being a caliber at a subsequent stage rolls the material to be rolled A(particularly, the flange corresponding parts 5, 6) thinner, andtherefore is more likely to remarkably cause a defective shape such asthe above-described occurrence of the flange wave. Further, if thedefective shape occurs, a step closer to the finish rolling is morelikely to be directly linked to the product defective shape. In otherwords, it is important to solve the problems as described above, inparticular, in the caliber 69 being a caliber at a subsequent stage fromthe viewpoint of the product dimension accuracy and the stability ofrolling.

In view of the problems, the present inventors have earnestly studiedabout the shapes of the calibers 59, 69 explained referring to FIG. 3and FIG. 4, and have arrived at the invention of the caliber shapesatisfying predetermined conditions causing no defective shape calledthe flange wave. Hereinafter, the detailed shape of a caliber 69′configured to cause no flange wave by further improving the shape of thecaliber 69 will be explained referring to the drawings. Note that thoughthe rolling and shaping relating to, in particular, the flangecorresponding part 6 of the caliber 69′ will be illustrated andexplained as an example in the following, the caliber of the object inthe present invention is a caliber for performing thickness reduction onthe whole material to be rolled A and is not limited to the calibers 59,69.

FIG. 7 is a schematic explanatory view of the caliber 69′ in theconfiguration obtained by modifying the above third caliber 69, and (a)illustrates a schematic entire view and (b) illustrates an enlarged viewnear a place facing the flange corresponding part 6 (a portionsurrounded by a broken line in FIG. 7(a)). Here, FIG. 7(b) illustratesan appearance after rolling in the caliber 69′ and illustrates therolled material to be rolled A with a one-dotted chain line. Note thatin FIG. 7, the same codes are given to components having the samefunctional configurations as those of the caliber 69 explained referringto FIG. 4 to omit explanation thereof.

In the modified caliber 69′ illustrated in FIG. 7, a facing portion 100facing the flange corresponding part 6 of the material to be rolled A isdifferent in shape from that of the above caliber 69 and is concretelycomposed of a plurality of flange facing portions 100 a, 100 b, 100 cdifferent in inclination in order to the side closer to the web.Regarding the flange facing portions 100 a, 100 b, 100 c, the flangefacing portion 100 b is prescribed and called as a “first flange facingportion”, and flange facing portions 100 a, 100 c arranged on both sidesthereof are prescribed and called a “second flange facing portion” and a“third flange facing portion” respectively in some cases in thisdescription. Further, a part of the flange corresponding part 6 rolledand shaped by the flange facing portion 100 b located at the middle isprescribed and called a “first flange part”, and parts of the flangecorresponding part 6 arranged on both sides thereof (parts to be rolledand shaped by the flange facing portions 100 a, 100 c) are prescribedand called a “second flange part” and a “third flange part” respectivelyin some cases.

Note that as illustrated in FIG. 7(a), a portion 101 facing the flangecorresponding part 5 of the material to be rolled A is similarlycomposed of flange facing portions 101 a, 101 b, 101 c.

Inclination angles of the flange facing portions 100 a, 100 b, 100 cwith respect to the horizontal line are θf2, θf1, θf3, respectively, andθf1 is an angle larger than θf2 and θf3. Besides, θf2 and θf3 may be anequal angle. When intervals tf2, tf1, tf3 (called also as roll gaps)between the upper caliber roll 65 and the lower caliber roll 68 in theflange facing portions 100 a, 100 b, 100 c are constant (the flangefacing portions 100 a, 100 b, 100 c of the upper caliber roll 65 and thelower caliber roll 68 are parallel), the angles θf2, θf1, θf3 in each ofthe upper caliber roll 65 and the lower caliber roll 68 are equal. Onthe other hand, when the angles formed between the flange facingportions 100 a, 100 b, 100 c and the horizontal line are differentbetween the upper caliber roll 65 and the lower caliber roll 68, it isonly necessary to regard average values of the angles formed between theflange facing portions of the upper caliber roll 65 and the lowercaliber roll 68 and the horizontal line as the angles θf2, θf1, θf3.Further, the inclination angles θf2, θf1, θf3 are substantially the sameeven when prescribed as angles formed between a center line S in theroll gap between the upper and lower rolls and the horizontal line.

Further, the flange facing portion 100 b is constituted at a positionacross a neutral line O in the height direction, and the flange facingportion 100 a is located on the side closer to the web than the flangefacing portion 100 b, and the flange facing portion 100 c is located onthe side closer to the arm (joint). In other words, the flange facingportion 100 b is located across the neutral line O and the flange facingportions 100 a, 100 c are located on both sides thereof.

Here, when the elongation per pass is defined by the thickness ratiobefore rolling to the thickness after rolling (after one pass), thethickness is represented by the roll gap in the sheet thicknessdirection in the caliber 69′, and a roll gap reduction amount in thevertical direction in one pass during reverse rolling in the caliber 69′is Δg, the elongations λf1, λf2, λf3 per pass of the flange facingportions 100 b, 100 a, 100 c are expressed by following Expressions (1)to (3).

λf1=tf1/tf1=(tf1+Δg·cos θf1)/tf1  (1)

λf2=tf2/tf2=(tf2+Δg·cos θf2)/tf2  (2)

λB=tf3/tf3=(tf3+Δg·cos θf3)/tf3  (3)

Note that tf1, tf2, tf3 are roll gaps corresponding to the thicknessbefore rolling of the flange corresponding part 6 corresponding to theflange facing portions 100 b, 100 a, 100 c in the caliber 69′. Further,tf1, tf2, tf3 are roll gaps corresponding to the thicknesses of theflange corresponding part 6 rolled by the flange facing portions 100 b,100 a, 100 c respectively in the caliber 69′.

Specifically, by making θf1 a larger angle than θf2 and θf3 based on therelation among tf1, tf2, tf3, the following Expressions (4), (5) aresatisfied in rolling in the caliber 69′.

λf1<λf2  (4)

λf1<λf3  (5)

Here, the above Expressions (1) to (3) express the elongations per passof rolling, and the relations similar to Expressions (1) to (3) areestablished also in the case of totaling the elongations in the reverserolling performed in a plurality passes. Accordingly, by making θf1 alarger angle than θf2 and θf3 in the caliber 69′, the above Expressions(4), (5) are satisfied not only in the case of the elongations per passbut also in the case of totaling the elongations in a plurality passesduring the reverse rolling.

The material to be rolled A rolled and shaped in the caliber 69′ becomesa bent shape having a plurality of inclination angles at the flangecorresponding part 5, 6. This shape is made into a desired flat flangeshape (flange shape of the hat-shaped steel sheet pile product) by thecaliber at a stage subsequent to the caliber 69′ provided in theintermediate rolling mill, for example, the fourth caliber 79, the fifthcaliber 89 in the finish rolling mill 30 (finish rolling step) or bothof the calibers. In the flange flattening, no reverse rolling isperformed. Note that after the bending-back of the flange part, streakytraces in the longitudinal direction are found in the boundary portionof the bent part due to the difference in adherence state of scale withrespect to other portions or the like, but the traces do not reduce thestrength or the like of the flange part and do not affect the quality asthe steel sheet pile.

According to the caliber configuration as illustrated in FIG. 7, makingthe angle On large decreases the flange elongation near the neutral lineO where the compressive stress is likely to occur relative to thecaliber 69 having the linear flange facing portion as illustrated inFIG. 4 and decreases the flange elongation near the neutral line Orelative to the flange elongation at a position separated from theneutral line O to thereby realize the effect of suppressing theoccurrence of the flange wave. On the other hand, making the angles θf2and θf3 small suppresses the increase in flange height to therebymaintain the elongation of the cross section of the flange correspondingpart 6. For example, it is only necessary to make the line length of thecenter line S corresponding to the flange facing portions (100 a, 100 b,100 c) of the caliber 69′ identical to the line length of the centerline of the flange facing portions of the caliber 69 and design theangles θf2, θf3 in a manner not to change the position in the horizontaldirection of the joint with respect to the angle On decided as a flangewave suppression condition, in consideration of the suppression ofvariation in dimension when shaping into a desired flat flange shape byrolling by the caliber at a subsequent stage. In other words, if thereverse rolling is performed in the modified caliber 69′, the flangeelongation decreases as compared with the caliber 69 illustrated in FIG.4 in the flange facing portion 100 b but the flange elongation increasesas compared with the caliber 69 at the flange facing portions 100 a, 100c, and therefore the same flange cross section elongation as that in thecaliber 69 can be maintained as the whole flange. Note that making theline length of the center line S corresponding to the flange facingportions (100 a, 100 b, 100 c) of the caliber 69′ identical to the linelength of the center line of the flange facing portions of the caliber69 does not mean being complete identical but may be being identicalwithin a range of error (for example, less than ±1% with respect to theline length of the center line of the flange facing portion).

Here, to suppress the flange wave at the flange facing portion 100 b(hereinafter, referred to also as a steep inclination part 100 b) nearthe neutral line O, it is preferable to set the angle θf1 so that therelation between the elongation λf1 of the flange at the steepinclination part 100 b and a elongation λw of the web corresponding part3 satisfies the following Expression (6).

λf1<λw  (6)

Note that it is preferable to set λf1/λw per pass to fall within a rangeof 0.967≤λf1/λw≤1.000, as a more detailed condition. The basis of thenumeral values will be explained in later-described examples.

Since the elongation of the flange is greatly affected by the elongationof the web, the elongation of the flange corresponding part near theneutral line O is expressed by the relation with the elongation of theweb also in the technique of the present invention. In the case of thehat-shaped steel sheet pile, the elongation of the arm correspondingparts 8, 9 and the elongation of the web corresponding parts 5, 6 areconsidered to be substantially equal, and since the U-shaped steel sheetpile has no arm corresponding part, the elongation of the flangecorresponding part near the neutral line O can be substantiallyexpressed by the relation with the web elongation. The elongation λw ofthe web in one pass during reverse rolling is expressed by the followingExpression (7).

λw=tw′/tw=(tw+Δg·cos θw)/tw  (7)

Here, tw′ is the roll gap corresponding to the thickness of the webcorresponding part 3 before rolling in the caliber 69′. Besides, tw isthe roll gap corresponding to the thickness of the web correspondingpart 3 rolled in the caliber 69′. Besides, θw is the inclination angleof the roll gap corresponding to the web corresponding part 3 withrespect to the horizontal line.

Further, in the case of the hat-shaped steel sheet pile having aconstant thickness in the flange width direction, the caliber shape isdesigned so that each thickness of the flange facing portions 100 a, 100b, 100 c is constant in the final pass except the error accompanyingroll abrasion or the like in the caliber 69′ directly before the finishrolling, but the inclination angle θf1 of the flange facing portion 100b is different from the inclination angles θf2, θf3 of the flange facingportions 100 a, 100 c, and therefore each thickness is not constant inmidway passes in the caliber 69′. For this reason, the inclination angleand the width of each flange facing portion may be decided inconsideration of the elongation ratios λf1/λw, λf2/λw, λf3/λw in a passwhere the flange wave is most likely to occur from the relation betweenthe thickness and elongation of each flange facing portion and theelongation of the web corresponding part.

As explained above, making the inclination angle θf1 of the steepinclination part 100 b large makes it possible to decrease the flangeelongation near the neutral line O and reduce the compressive stressoccurring at this portion.

Making the caliber shape of the caliber 69′ provided in the secondintermediate rolling mill 19 in the shape having the plurality of flangefacing portions 100 a, 100 b, 100 c different in inclination asexplained above referring to FIG. 7 and setting the inclination anglesof the flange facing portions 100 a, 100 b, 100 c to preferableconditions as expressed in the above Expressions (1) to (6) make itpossible to reduce the compressive stress occurring near the neutralline O of the flange corresponding part 6 in the rolling and shaping inthe caliber 69′ and suppress the occurrence of the flange wave.Furthermore, it is also possible to reduce the restoration of the flangethickness occurring due to gathering of the metal near the neutral lineof the flange corresponding part 6 in the reverse rolling to furthersuppress the occurrence of the flange wave.

On the other hand, the elongation of the flange occurring at the flangefacing portions 100 a and 100 c increases relative to the elongation ofthe flange occurring near the neutral line O (namely, the elongation ofthe flange at the flange facing portion 100 b) and the compressivestress occurring there also increases, but the compressive stress doesnot become excessive since metal flow to the web corresponding part 3and the arm corresponding part 9 is likely to occur in addition toseparation from the neutral line O. Further, parts, corresponding to theflange facing portions 100 a and 100 c, in the flange corresponding part6 are connected to the web corresponding part 3 and the armcorresponding part 9 and unlikely to cause buckling, so that the flangewave is unlikely to occur at the parts.

As described above, making the caliber shape of the caliber 69′ in theshape having the plurality of flange facing portions 100 a, 100 b, 100 cdifferent in inclination angle makes it possible to suppress the flangewave occurring near the neutral line O of the flange corresponding parts5, 6 of the material to be rolled A as compared with the rolling andshaping in the conventional caliber shape (caliber 69) as illustrated inFIG. 4, thereby realizing the improvement of the product dimensionaccuracy and the stability of rolling. Depending on the product shape,the elongation of the flange corresponding parts 5, 6 is larger than theelongation of the web corresponding part 3 in the conventional calibershape (caliber 69) as illustrated in FIG. 4, so that the balance cannotbe maintained any longer and the flange wave cannot be suppressed insome cases. In this case, not changing the inclination angle of thewhole flange but making the inclination angle θf1 of the steepinclination part 100 b larger than the flange inclination angle of theconventional caliber shape as illustrated in FIG. 7 and larger than theflange facing portions 100 a and 100 c makes it possible to suppress theincrease in height of the material to be rolled A during the rolling andshaping and effectively suppress the flange wave.

One example of the embodiment of the present invention has beenexplained above, but the present invention is not limited to theillustrated embodiment. It should be understood that various changes andmodifications are readily apparent to those skilled in the art withinthe scope of the spirit as set forth in claims, and those should also becovered by the technical scope of the present invention.

For example, the technique of the present invention is applied in theabove embodiment, and the explanation has been made using the thirdcaliber 69 as the object to be modified in caliber shape and especiallythe rolling and shaping of the flange corresponding part 6 of thematerial to be rolled A has been explained referring to FIG. 7, but theapplication range of the present invention is not limited to this. Morespecifically, the technique of the present invention is obviouslyapplicable to both of the flange corresponding parts 5, 6 in the rollingand shaping in the third caliber 69 and also to the rolling and shapingin the second caliber 59. More specifically, the same modification canbe applied also to the caliber 59 explained referring to FIG. 3 tosuppress, for example, the flange wave occurring in the firstintermediate rolling. Further, as a matter of course, the technique ofthe present invention may be applied to the caliber shapes of both ofthe second caliber 59 and the third caliber 69. Alternatively, regardingthe second caliber 59 and the third caliber 69 for mainly reducing thethickness, the same modification may be applied also to the case wherethe second caliber 59 is made into a caliber shape having both endportions in the width direction opened and the third caliber 69 is madeinto a caliber shape for simultaneously performing the shaping of theclaw height. Furthermore, the technique of the present invention may beapplied to the first caliber for performing the rough rolling.

Further, though the caliber shape of the caliber 69′ is explained as ashape having the plurality of flange facing portions 100 a, 100 b, 100 cdifferent in inclination angle in the above embodiment, the importantpoint of the technique of the present invention is to make theinclination angle θf1 of the flange facing portion 100 b near theneutral line O larger than those of the other flange facing portions inthe caliber for performing the intermediate rolling so as to reduce thecompressive stress acting on the material to be rolled A near theneutral line O. From the viewpoint, in the case of constituting thecaliber of the intermediate rolling mill in a shape having the pluralityof flange facing portions different in inclination angle in thetechnique of the present invention, it is not always to provide thethree flange facing portions as illustrated in FIG. 7, but any number offlange facing portions different in inclination angle may be provided aslong as the inclination angle θf1 of the flange facing portion 100 bnear the neutral line O is larger than those of the other flange facingportions. In short, for example as illustrated in FIG. 10, the caliberfor performing the intermediate rolling may be configured to have fouror more flange facing portions different in inclination angle.

Further, the caliber part facing the flange corresponding part 5, 6 ofthe material to be rolled A (namely, the flange facing portion 100) maybe, with respect to a straight line linking the boundary part on the armside (of the material to be rolled) and the boundary part on the webside (of the material to be rolled), in a protruding shape in a flangeinside direction on the side closer to the arm than the flange facingportion near the neutral line O and in a protruding shape in a flangeoutside direction on the side closer to the web than the flange facingportion near the neutral line O.

Specifically, regarding the shape of the flange facing portion 100provided with the steep inclination part 100 b explained in the aboveembodiment, the shape of each of the flange facing portions 100 a to 100c does not always need to be formed in the linear shape but, forexample, part or all of the flange facing portions 100 a to 100 c may beformed by a curved line as long as the inclination angles of the flangefacing portions 100 a, 100 b, 100 c are made under the preferableconditions as expressed in the above Expressions (4) to (6). In thiscase, the steep inclination part 100 b is defined as a range sandwichedbetween an intersection with the flange facing portion 100 a and anintersection with the flange facing portion 100 c, and the steepinclination part 100 b is configured to cross the neutral line O.

FIG. 8 is a schematic explanatory view according to a modificationexample of the present invention and is a schematic enlarged viewillustrating an example of the vicinity of a place facing the flangecorresponding part 6. As illustrated in FIG. 8, in this modificationexample, the flange facing portions 100 a, 100 c are formed in a curvedshape. The step of performing the reverse rolling, including otherembodiments, preferably includes a step of forming the web correspondingpart 3 connected to the flange part including at least one second flangepart (referred to also as a web-side flange part) and the armcorresponding part 9 connected to the flange part including at least onethird flange part (referred to also as an arm-side flange part). In thiscase, the caliber according to the present invention preferably includesa web facing portion 100 d for forming the web corresponding part 3 andan arm facing portion 100 e for forming the arm corresponding part 9.Here, the caliber preferably includes a web-side flange facing portiongroup including at least one flange facing portion 100 a (second flangefacing portion) and an arm-side flange facing portion group including atleast one flange facing portion 100 c (third flange facing portion).Here, the boundary between the web-side flange facing portion group andthe web facing portion 100 d is assumed to be Pa, and the boundarybetween the arm-side flange facing portion group and the arm facingportion 100 e is assumed to be Pc. In the example illustrated in FIG. 8,with respect to a straight line Q linking the boundary part Pc on thearm side (the boundary between the arm facing portion 100 e facing thearm corresponding part 9 and the flange facing portion 100 c) and theboundary part Pa on the web side (the boundary between the web facingportion 100 d facing the web corresponding part 3 and the flange facingportion 100 a in the caliber 65), the flange facing portion 100 a is ina curved shape to be a protruding shape in a flange outside direction,and the flange facing portion 100 c is in a curved shape to be aprotruding shape in a flange inside direction. Further, the steepinclination part 100 b is illustrated as a linear shape in thismodification example, but the steep inclination part 100 b may be in acurved shape.

In the case where the flange facing portions 100 a, 100 c as illustratedin FIG. 8 are in a curved shape, the inclination angles θf2, θf3 of theflange facing portions 100 a, 100 c only need to be decided by theinclination angles of the tangents (Qa, Qc in FIG. 8) at the middle partin the height direction of the flange facing portions 100 a, 100 c withrespect to the horizontal line. In the case where the steep inclinationpart 100 b is in a curved shape, the inclination angle only needs to bedecided based on the tangent where the angle becomes maximum. Thestraight line Q and the tangents Qa, Qc are explained using the lowercaliber roll 68 in FIG. 8, and those only need to be similarly decidedalso in the upper caliber roll 65. Then, in the case where the anglesformed between the flange facing portions 100 a, 100 b, 100 c and thehorizontal line are different between the upper caliber roll 65 and thelower caliber roll 68, θf2, θf2, θf3 only need to be set to averagevalues of the angles formed between the flange facing portions of theupper caliber roll 65 and the lower caliber roll 68 and the horizontalline. By setting the inclination angles of the flange facing portions100 a to 100 c defined as described above to the preferable conditionsas expressed in the above Expressions (1) to (6) similarly to the aboveembodiment, the same operation and effect can be obtained.

More specifically, in the above embodiment, the caliber shape of themodified caliber 69′ is explained as a shape having the plurality offlange facing portions 100 a, 100 b, 100 c different in inclinationangle, but the detailed shapes of the portions 100 a, 100 b, 100 c arenot mentioned. The shape of the flange corresponding part 5, 6 onlyneeds to be constituted by a plurality of straight lines or curved linesor combination of them, and the shapes of the portions 100 a, 100 b, 100c can be arbitrarily designed according to the shape of the flangecorresponding part 5, 6. If the curved portion is constituted in theflange corresponding part 5, 6, the inclination angle of the curvedportion only needs to be defined by the angle of its tangent.

Further, it is extremely effective to apply the technique of the presentinvention to a product in which the flange corresponding part has athickness distribution that the thickness changes in a direction alongthe surface of the flange corresponding part or to a product in a shapehaving a plurality of bent portions in which the flange correspondingpart increases in inclination angle near the neutral line, which fallswithin the scope of the present invention. In the case where the flangecorresponding part has the thickness distribution in a direction alongits surface, it is conceivable to relatively decrease the thickness nearthe neutral line based on the cross-sectional efficiency of thehat-shaped steel sheet pile product. When applying the technique of thepresent invention to the above case, the elongation of the flange in theflange facing portion 100 b is unlikely to become larger than that inthe conventional caliber shape because the inclination angle of theflange facing portion 100 b is larger than the those of the flangefacing portions 100 a, 100 c, so that the operation and effect equal toor more than those in the above embodiment can be obtained. Further, therolling states in the bent shapes illustrated in FIG. 7 and FIG. 8 canbe applied also to the steel sheet pile product in which the flange isbent to increase in inclination angle near the neutral line in theproduct shape, which is very useful.

Further, in the caliber shape of the caliber 69′, the boundary partsbetween the flange facing portions 100 a, 100 b, 100 c may have R. Inthis case, each boundary between the flange facing portions 100 a, 100b, 100 c only needs to be an intermediate point of a corner R.

Furthermore, as a result of detailed study by the present inventors, ithas been revealed that the flange wave occurring in the conventionalcaliber 69 has a peak position of the wave height in the cross sectionof the flange corresponding part included in a range of 10% of a caliberdepth D in the height direction from the neutral line O of the caliber69 illustrated in FIG. 4.

Therefore, in the case where the steep inclination part 100 b near theneutral line O is linear, it is desirable that the steep inclinationpart 100 b decreasing the flange elongation includes the range of 10% ofthe caliber depth D in the height direction upward and downward from theneutral line O as illustrated in FIG. 11. Further, when a center pointposition Fc of a line segment in the steep inclination part 100 b of thecenter line S coincides with the neutral line O, the operation andeffect explained in the above embodiment can be remarkably obtained.Note that the caliber depth D is defined by the height in the verticaldirection of the whole flange facing portions (100 a, 100 b, 100 c) ofthe lower caliber roll forming the caliber, and the upper end positionof the caliber depth D is the upper end in the height direction of theboundary between the flange corresponding part and the arm correspondingpart, and the lower end position is the lower end in the heightdirection of the boundary between the flange corresponding part and theweb corresponding part as illustrated in FIG. 11.

Further, also in the case where the flange facing portion 100 b near theneutral line O is curved or a combination of a plurality of linesegments, it is desirable that the steep inclination part 100 b (a rangeof P1 to P2 in the elongation) includes the range of 10% of the caliberdepth D in the height direction upward and downward from the neutralline O as illustrated in FIG. 12. In these cases, when a position Fdwhere the angle with respect to the horizontal line becomes maximum inthe line segment corresponding to the steep inclination part 100 b ofthe center line S coincides with the neutral line O, the above-describedeffect is further remarkable. However, as illustrated in FIG. 12, evenif the position Fd deviates in the height direction from the neutralline O as long as it is within the range of 10% of the caliber depth D,the effect of the present invention can be provided. This is because ofthe same reason as that in the case where the flange facing portion 100b is linear. In this case, it is only necessary to set the inclinationangle at the position of the maximum inclination angle to θf2 and setthe flange elongation to λ1. Accordingly, these cases are also regardedas being near the neutral line O and fall within the scope of thepresent invention.

Note that the case where the second flange facing portion and the thirdflange facing portion are arranged adjacent to the first flange facingportion is explained in the above embodiment and other embodiments, butthey do not always need to be adjacently arranged. In other words, thesecond flange facing portion and the third flange facing portion aresmaller in inclination angle than the first flange facing portion, andcan also be set according to the product shape between the first flangefacing portion and the web facing portion and between the first flangefacing portion and the arm facing portion, respectively.

Further, the above embodiment and other embodiments have beenillustrated and explained using the case of rolling the hat-shaped steelsheet pile as an example, but the application range of the presentinvention is not limited to them. In other words, the present inventionis applicable to steel sheet piles with flanges in various shapes wherethe flange wave possibly occurs in the intermediate rolling. Morespecifically, the present invention is applicable to a U-shaped steelsheet pile in addition to the hat-shaped steel sheet pile.

EXAMPLES Example 1

As Example 1 of the present invention, a caliber corresponding to themodified caliber 69′ above explained referring to FIG. 7 was applied tothe intermediate rolling caliber (the second caliber and the thirdcaliber in the above embodiment), and the rolling and shaping wasperformed on the material to be rolled under the conditions 1 to 5listed in the following Table 1.

The flange facing portion of the caliber was configured to be bent tothree portions such that the first flange part crossed the neutral lineof the calibers indicated in the conditions 1 to 5. Here, the angle andthe length of each flange facing portion were adjusted. Further, theflange facing portion of the material to be rolled after the rolling andshaping was flattened in the calibers at the subsequent stages (thefourth caliber and the fifth caliber in the above embodiment).

Further, as comparative examples, the conventional caliber (a calibercorresponding to the caliber 69 before modification) was applied to theintermediate rolling caliber, and the rolling and shaping was performedon the material to be rolled under the conditions 6, 7 listed in thefollowing Table 1.

The rolling and shaping in the caliber under each of the conditionsindicated in the conditions 1 to 7 is performed in a plurality ofpasses, and the flange/web elongation ratios λf1/λw, λf2/λw, λf3/λwlisted in Table 1 are elongation ratios per pass of the rolling andshaping in the plurality of passes. Note that in the examples andcomparative examples, the flange angle θf of the hat-shaped steel sheetpile product as the final product to be produced was set to 48°. FIG. 9is an explanatory view of this example, and is a schematiccross-sectional view illustrating an appearance of the final pass of therolling and shaping in the third caliber according to the example. Notethat FIG. 9 illustrates, using a broken line, the shape of the flangefacing portion having a flange angle θf=48° similar to the finalproduct. The values of codes θf1, θf2, θf3 listed in Table 1 are valuesat places illustrated in FIG. 9.

TABLE 1 PRODUCT FLANGE FLANGE ANGLE(°) λf2/λw CONDITION THICKNESS(mm)θf1 θf2 θf3 λf1/λw λf3/λw RESULT 1 PRESENT 6.5 66 44 44 0.967 1.020 NOFLANGE INVENTION WAVE OCCURRED 2 PRESENT 6.5 60 45 45 0.985 1.018 NOFLANGE WAVE INVENTION OCCURRED 3 PRESENT 6.5 56 42 42 0.995 1.023 NOFLANGE WAVE INVENTION OCCURRED 4 PRESENT 6.5 54 45 45 1.000 1.018 NOFLANGE WAVE INVENTION OCCURRED 5 PRESENT 6.5 52 45 45 1.004 1.018 LITTLEFLANGE INVENTION WAVE DURING INTERMEDIATE ROLLING (NO FLANGE WAVE ONPRODUCT) 6 CONPARATIVE 6.5 48 1.013 FLANGE WAVE EXAMPLE OCCURRED 7CONPARATIVE 7.7 48 0.995 FLANGE WAVE EXAMPLE OCCURRED

As listed in Table 1, under the conditions 1 to 5, the values of anglesθf1, θf2, θf3 were changed as in Table 1 when forming the steepinclination part in the caliber and the intermediate rolling wasperformed under each of the conditions. Then, the flange correspondingpart of the material to be rolled subjected to the rolling and shapingunder of each of the conditions was then shaped into a linear shape(flat shape) in the rolling mill at the subsequent stage, and thedefective shape such as the presence or absence of the occurrence of theflange wave was confirmed.

Under the conditions 1 to 5, the steep inclination part having θf1>θf2,θf1>θf3 was formed in the caliber, resulting in λf1<λf2, λf1<λf3, andthe value of λf1/λw is 0.967 to 1.004. Under the above condition, theflange elongation at the steep inclination part was reduced to suppressthe occurrence of the flange wave. Regarding the conditions 1 to 4, thevalue of λf1/λw is 0.967 to 1.000 so as to satisfy the above Expression(6), thus it was confirmed that there was no occurrence of the flangewave from the intermediate rolling time. Further, regarding thecondition 5, the value slightly deviated from the range of the aboveExpression (6), little flange wave was confirmed in some passes duringthe intermediate rolling time, but no flange wave was confirmed in theproduct passed through the rolling at the subsequent stage and the like,and thus sufficient effect was confirmed.

On the other hand, under the condition 6 (comparative example), therolling and shaping was performed without forming the steep inclinationpart in the caliber, resulting in flange elongation λf1>web elongationλw, and the rolling and shaping was rolling and shaping not satisfyingthe Expression (6) explained in the above embodiment, in which theoccurrence of the flange wave was confirmed.

Further, under the condition 7 (comparative example), the flangethickness of the product was increased by 1.2 mm and rolling wasperformed under the condition of the value of λf1/λw of 0.995 to satisfythe Expression (6), but the rolling and shaping was performed withoutforming the steep inclination part as in the condition 6, and thus theoccurrence of the flange wave was confirmed.

In short, in the comparative examples under the conditions 6, 7, therolling and shaping was performed without forming the steep inclinationpart in the caliber under the condition that the inclination angle ofthe flange part was constant at any position, and thus the elongationwas different depending on the position (part) of the flange part andthe flange wave occurred.

From the above, it is found that bending the flange facing portion ofthe caliber into three portions suppresses the occurrence of the flangewave to enable the production in a size with small flange thickness.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a production technique of a steelsheet pile having a flange such as a hat-shaped steel sheet pile, aU-shaped steel sheet pile and the like.

EXPLANATION OF CODES

-   -   1 . . . rolling facility    -   3 . . . web corresponding part    -   5, 6 . . . flange corresponding part    -   8, 9 . . . arm corresponding part    -   10, 11 . . . joint corresponding part    -   14, 15 . . . claw part    -   17 . . . rough rolling mill    -   18 . . . first intermediate rolling mill    -   19 . . . second intermediate rolling mill    -   30 . . . finish rolling mill    -   45 . . . upper caliber roll (of first caliber)    -   48 . . . lower caliber roll (of first caliber)    -   49 . . . first caliber    -   55 . . . upper caliber roll (of second caliber)    -   58 . . . lower caliber roll (of second caliber)    -   59 . . . second caliber    -   65 . . . upper caliber roll (of third caliber)    -   68 . . . lower caliber roll (of third caliber)    -   69 . . . third caliber    -   69′ . . . modified third caliber    -   75 . . . upper caliber roll (of fourth caliber)    -   78 . . . lower caliber roll (of fourth caliber)    -   79 . . . fourth caliber    -   85 . . . upper caliber roll (of fifth caliber)    -   88 . . . lower caliber roll (of fifth caliber)    -   89 . . . fifth caliber    -   100 . . . facing portion    -   100 a to 100 c . . . flange facing portion    -   101 a to 101 c . . . flange facing portion    -   A (A1 to A5) . . . material to be rolled    -   L . . . rolling line    -   O . . . neutral line

1. A production method for forming a steel sheet pile with flanges froma material to be rolled by caliber roll rolling, the production methodcomprising a step of performing reverse rolling on the material to berolled by a same caliber, wherein: the step of performing reverserolling comprises a step of forming first flange parts across a neutralline and second and third flange parts arranged on both sides of thefirst flange parts; the caliber comprises first flange facing portionsfor forming the first flange parts, second flange facing portions forforming the second flange parts, and third flange facing portions forforming the third flange parts; and an inclination angle of the firstflange facing portion with respect to a horizontal plane is larger thaninclination angles of the second and third flange facing portions. 2.The production method for a steel sheet pile with flanges according toclaim 1, wherein: the step of performing reverse rolling comprises astep of forming a web corresponding part and arm corresponding parts;the caliber comprises a web facing portion for forming the webcorresponding part and arm facing portions for forming the armcorresponding parts; the caliber comprises web-side flange facingportion groups each including at least one of the second flange facingportions and arm-side flange facing portion groups each including atleast one of the third flange facing portions; and with respect to astraight line linking a boundary part between the web-side flange facingportion group and the web facing portion and a boundary part between thearm-side flange facing portion group and the arm facing portion, thesecond flange facing portion is in a protruding shape in a flangeoutside direction, and the third flange facing portion is in aprotruding shape in a flange inside direction.
 3. The production methodfor a steel sheet pile with flanges according to claim 1, whereinrolling in which a flange elongation λf1 at the first flange part issmaller than flange elongations λf2, λf3 at the second flange part andthe third flange part is performed in the caliber.
 4. The productionmethod for a steel sheet pile with flanges according to claim 1, whereinthe step of forming the first flange parts, the second flange parts, andthe third flange parts is an intermediate rolling step.
 5. Theproduction method for a steel sheet pile with flanges according to claim4, wherein the caliber has a caliber shape opened at both end parts in awidth direction.
 6. The production method for a steel sheet pile withflanges according to claim 1, wherein the flange corresponding parts ina bent shape formed in the material to be rolled by the step of formingthe first flange parts, the second flange parts, and the third flangeparts are rolled and shaped into a desired flat shape by rolling in acaliber at a stage subsequent to the step of forming the first flangeparts, the second flange parts, and the third flange parts.
 7. Theproduction method for a steel sheet pile with flanges according to claim1, wherein rolling is performed in the caliber so that the flangeelongation λf1 at the first flange part becomes a web elongation λw orless.
 8. The production method for a steel sheet pile with flangesaccording to claim 1, wherein the steel sheet pile is a hat-shaped steelsheet pile.
 9. A production facility for forming a steel sheet pile withflanges from a material to be rolled by caliber roll rolling, theproduction facility comprising a rolling mill which performs reverserolling on the material to be rolled by a same caliber, wherein: therolling mill which performs reverse rolling comprises a caliber whichforms first flange parts across a neutral line and second and thirdflange parts arranged on both sides of the first flange parts; thecaliber comprises first flange facing portions for forming the firstflange parts, second flange facing portions for forming the secondflange parts, and third flange facing portions for forming the thirdflange parts; and an inclination angle of the first flange facingportion with respect to a horizontal plane is larger than inclinationangles of the second and third flange facing portions.
 10. Theproduction facility for a steel sheet pile with flanges according toclaim 9, wherein: the rolling mill which performs reverse rollingcomprises a caliber which forms a web corresponding part and armcorresponding parts; the caliber comprises a web facing portion forforming the web corresponding part and arm facing portions for formingthe arm corresponding parts; the caliber comprises web-side flangefacing portion groups each including at least one of the second flangefacing portions and arm-side flange facing portion groups each includingat least one of the third flange facing portions; and with respect to astraight line linking a boundary part between the web-side flange facingportion group and the web facing portion and a boundary part between thearm-side flange facing portion group and the arm facing portion, thesecond flange facing portion is in a protruding shape in a flangeoutside direction, and the third flange facing portion is in aprotruding shape in a flange inside direction.
 11. The productionfacility for a steel sheet pile with flanges according to claim 9,wherein a flange elongation λf1 at the first flange part is smaller thanflange elongations λf2, λf3 at the second flange part and the thirdflange part in the caliber.
 12. The production facility for a steelsheet pile with flanges according to claim 9, wherein the caliber is acaliber provided in an intermediate rolling mill.
 13. The productionfacility for a steel sheet pile with flanges according to claim 12,wherein the caliber has a caliber shape opened at both end parts in awidth direction.
 14. The production facility for a steel sheet pile withflanges according to claim 9, further comprising a subsequent-stagecaliber which rolls and shapes the flange corresponding parts in a bentshape formed in the material to be rolled by rolling in the caliberwhich forms the first flange parts, the second flange parts, and thethird flange parts, into a desired flat shape.
 15. The productionfacility for a steel sheet pile with flanges according to claim 9,wherein the flange elongation λf1 at the first flange part is a webelongation λw or less in the caliber.
 16. The production facility for asteel sheet pile with flanges according to claim 9, wherein the steelsheet pile is a hat-shaped steel sheet pile.